Not according to this report:
http://www2.ljworld.com/news/2001/sep/12/towers_built_to/
“I designed it for a 707 to smash into it.”
The other structual engineer, John Skilling, also contends the buildings should have withstood the impact.
“The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707—DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.”
-John Skilling, one of the two structural engineers responsible for designing the Trade Center.